1. Field of the Invention
The invention relates to a method for granulating liquid slag melts, in particular blast furnace slag, wherein the melt is ejected into a cooling chamber via a slag tundish and wherein fluid under pressure, in particular compressed gas, vapor or pressurized water, is injected in the direction of the slag exit in order to eject said liquid slag, as well as a device for carrying out this method.
2. Prior Art
In order to granulate and disintegrate molten slags, it has already been proposed to eject the same into granulation spaces by the aid of vapor or a propellant with further comminution subsequently being effected also in jet mills using propellant jets. Based on slag temperatures of between 1400.degree. and 1600.degree. C., the relatively large temperature difference between the propellant gas stream and the molten slag involves the risk of the formation of more or less large agglomerates as well as the danger of thread formation, which will consequently increase the comminution work and considerably reduce the cooling rate. The proposals made so far were primarily based on the object to accomplish the cooling of the molten slags as rapidly as possible, such proposals having, of course, been impaired by the formation of agglomerates and threads.
According to another unpublished proposal made by the Applicant, the liquid slag was ejected into the granulation space by the aid of combustion offgases in order to reduce the danger of the slag exit opening from the slag tundish to be obstructed by solidifying slag. By such a mode of procedure, the slag particles injected into the granulation space get into a consecutively arranged cooling zone at substantially higher temperatures, which higher temperatures bring about a reduced slag viscosity and a reduced surface tension of the slag droplets such that a finer division of the slag droplets is being obtained as the latter enter the cooling zone. The fine dispersion of slag droplets results in accordingly small droplets having relatively high specific surfaces such that cooling may be achieved in smaller-structured cooling chambers. Yet, the installation of burners in the region of the slag spout of the tundish involves high structural and apparative expenses.